# Le Chatelier's Principle: Equilibrium Shift with Pressure Change

• youmei0426
In summary, the equilibrium between H+(aq) and HCO3-(aq) will shift to the side with fewer moles of molecules when the pressure is increased according to le Chatelier's principle. However, this is only true for gases, not in general. It is important to consider the states of all substances present and how they will be affected by the change in pressure. Instead of focusing on the vague concept of the equilibrium shifting to the left or right, it is more helpful to think about the equilibrium constant and the concentration of water in the system.
youmei0426

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## The Attempt at a Solution

I know that the equilibrium will shift to the side with fewer moles of molecules when the pressure is increased according to le Chatelier's principle, so I thought in this case it would shift to the left as there is only 1 mole of gaseous atom compared to 2 moles on the right-hand side. The answer is A, however. Thanks in advance!

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H+(aq) and HCO3-(aq) are ions in the aqueous solution.

youmei0426
youmei0426 said:
I know that the equilibrium will shift to the side with fewer moles of molecules when the pressure is increased

As worded it is true for gases only, not in general.

As @Lord Jestocost already hinted, check state of all present substances. How many are gases?

youmei0426
Time to say after half a century I have always hated from the very beginning this expression "The equilibrium shifts to the left (or the right)." I at first indeed did not know what that meant, well I picked it up from the way the teacher repeatedly used it, but I do not think it is good wording. That said, you will meet it.

The way I think is, there is something that is constant, the equilibrium constant.
In this example there is another thing that you can take as constant, the concentration of water.
That being so, and looking at your equation and looking also the corresponding equation that defines the equilibrium constant, when the pressure of CO2 increases, what else must change and how?

I think that is a better way of thinking than being bamboozled by words.

Last edited:
youmei0426 and Bystander

## 1. What is Le Chatelier's Principle?

Le Chatelier's Principle states that when a system at equilibrium is subjected to a change in conditions, the system will shift in a direction that minimizes the effect of the change.

## 2. How does a change in pressure affect equilibrium?

A change in pressure will affect equilibrium by causing the system to shift in the direction that reduces the pressure. This is because an increase in pressure will favor the side with fewer moles of gas, while a decrease in pressure will favor the side with more moles of gas.

## 3. What happens to equilibrium when pressure is increased?

When pressure is increased, the equilibrium will shift in the direction that reduces the pressure. This means that the reaction will favor the side with fewer moles of gas.

## 4. How does a change in volume affect equilibrium?

A change in volume will affect equilibrium in a similar way to a change in pressure. An increase in volume will favor the side with more moles of gas, while a decrease in volume will favor the side with fewer moles of gas.

## 5. Can Le Chatelier's Principle be applied to all equilibrium reactions?

Yes, Le Chatelier's Principle can be applied to all equilibrium reactions, as long as the reaction is reversible and the conditions are changed. This principle is a fundamental concept in chemistry and is used to predict and understand the behavior of chemical reactions at equilibrium.

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